UPGRADING REPAIRING PCs

Other Add-On Card Configuration Issues 53
system are designed to automatically move to non-conflicting settings
when less-flexible PnP cards are inserted. Late-model
Pentium-class systems using Windows 95 OSR 2.x, Windows 98,
Windows 2000, or Windows Me can also use an IRQ holder for PCI
steering feature that allows multiple PCI devices to use a single
IRQ, if the BIOS is designed to support it.
To view the current IRQ and DMA settings for systems using
Windows 9x, use the Device Manager (a tab on the System
Properties sheet). View the properties for the “Computer” icon at
the top of the device list and you can choose from IRQ, DMA, I/O
port, and Memory address information (see Figure 2.15).
Figure 2.15 The Windows 9x Device Manager and Computer Properties
sheet shows IRQs in use; available IRQs are not listed. The IRQ steering feature
enables IRQ 5 to be shared between two different PCI-based cards without
conflicts.
For other operating systems, I recommend an interface card with
signal lights for IRQ and DMA usage. The Discovery Card, developed
by John Rourke, pioneered this diagnostic category, and many
vendors offer cards with this feature. Some vendors combine
IRQ/DMA detection with POST code detection or active system
testing.
To use an IRQ/DMA card, turn off the system, insert the card into
an open slot, and turn on the system. As devices that use an IRQ or
a DMA are activated, the corresponding signal light on the card is
displayed. Most cards have a reset switch, which enables the card
lights to be cleared, allowing you to test for possible conflicts. When
combined with information from a system configuration template,
this helps provide accurate IRQ and DMA usage information.